21275686409 has 2 divisors, whose sum is σ = 21275686410. Its totient is φ = 21275686408.

The previous prime is 21275686349. The next prime is 21275686429. The reversal of 21275686409 is 90468657212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16034650384 + 5241036025 = 126628^2 + 72395^2 .

It is a cyclic number.

It is not a de Polignac number, because 21275686409 - 2¹² = 21275682313 is a prime.

It is not a weakly prime, because it can be changed into another prime (21275686429) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10637843204 + 10637843205.

It is an arithmetic number, because the mean of its divisors is an integer number (10637843205).

Almost surely, 2^21275686409 is an apocalyptic number.

It is an amenable number.

21275686409 is a deficient number, since it is larger than the sum of its proper divisors (1).

21275686409 is an equidigital number, since it uses as much as digits as its factorization.

21275686409 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1451520, while the sum is 50.

The spelling of 21275686409 in words is "twenty-one billion, two hundred seventy-five million, six hundred eighty-six thousand, four hundred nine".